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प्रश्न
State two properties that a substance should possess when used as a thermionic emitter.
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उत्तर
Two properties are:
(i) High melting point. (ii) Low work function.
संबंधित प्रश्न
How can they be made to leave the metal surface? (State any two ways)
Arrange α, β, and γ rays in ascending order with respect to their
1) Penetrating power.
2) Ionising power
3) Biological effect
In following fig. shows a mixed source S of alpha and beta particles in a thick lead container. The particles pass through a magnetic field in a direction perpendicular to the plane of paper (inwards as shown by x). State and show in the diagram how the particles get affected.
Radioactive substances were found to give off three types of rays. Name them. How do they
(a) React to the magnetic field?
(b) React to the electric field?
(c) Act when different thickness of lead sheets is placed in their path?
An element P disintegrates by α - -emission and the new element suffers two further disintegrations, both by β -emission, to form an element Q. Explain the fact that P and Q are the isotopes.
During the emission of a beta particle, the ______ number remains same.
What is meant by Radioactivity?
Mention four properties of Becquerel rays.
The half-life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours would be ______.
In U238 ore containing Uranium the ratio of U234 to Pb206 nuclei is 3. Assuming that all the lead present in the ore is final stable product of U238. Half life of U238 to be 4.5 × 109 years and the age of ore is ______ × 109 years. (in 109 years)
